1. Field of the Invention
The present invention relates to highly absorbent, water-insoluble carboxymethyl cellulose foam, which expands in volume when absorbing liquid or water, but does not gelate, and maintains shape.
2. Description of the Related Art
Carboxymethyl cellulose, usually called CMC, is a cellulose derivative in which the hydroxyl groups of glucose, which makes up the cellulose backbone, are substituted with carboxymethyl groups. CMC is used in various fields including glues, foods, cosmetics, additives for pharmaceutical drugs, petroleum drilling, etc., and in particular, it is widely used in medical products due to its excellent biocompatibility.
Examples of medical applications of CMC include adhesion barriers, wound healing agents, hemostatic agents, etc. Importantly, adhesion barriers should be decomposed after a certain period of time once they are inserted into the body, whereas wound healing agents and hemostatic agents for external wound, should maintain their shapes for a certain period of time without being decomposed. Accordingly, water-insolubility is a prerequisite for use as external wound healing agents or hemostatic agents.
Importantly, CMC foam should have high degree of liquid absorption for a medical use. In the case of a moisture wound dressing, it is important to effectively absorb body fluids produced during wound healing, and the foam to be used for this purpose should be highly absorbent. For a hemostatic dressing, the foam to be used for this purpose should also be highly absorbent in order to sufficiently absorb the blood being released.
Additionally, when the CMC foam absorbs liquid it is desirable that the CMC foam expands in volume while maintaining its shape. The volumetric expansion due to the absorption of body fluids during a wound healing process can reduce the dead space between a wound dressing and the wound surface, and therefore prevent invasion of infectious agents, such as bacteria, into the wound surface. Additionally, in the case of a cavity dressing, the dressing size is preferably small for easy insertion into the wound cavity. The dressing, once correctly placed on the cavity, can absorb body fluids or a saline solution to expand its volume, thereby filling up the cavity. If used as a hemostatic agent, the dressing can expand its volume by absorbing blood, thereby compressing blood vessels and promoting hemostasis.
Accordingly, for medical use of the CMC foam, and in particular, for its use as a wound healing agent or a hemostatic agent, it is important that the CMC foam has the properties of water-insolubility, high degree of liquid absorption, and high expansibility. However, the CMC foams known so far had problems in that they have a poor expansibility of about 1.5-fold (150%) or they gelate after absorbing a liquid and are thus unable to maintain their shapes.
For example, Korean Patent No. 10-0588614 and Japanese Patent Application Publication No. 2010-284216 describe anti-adhesion agents comprising CMC as an active ingredient. However, CMC was used as an anti-adhesion agent in the above patent documents, and it is not suitable for use as a wound healing agent or a hemostatic agent because it decomposes after a certain period of time when inserted into the body, and gelates when absorbing a liquid.
Additionally, Korean Patent Application Publication No. 2002-0062301 describes a tissue-coating medical material made of a soluble cellulose derivative that has been made hardly soluble in water. However, this patent document fails to describe the liquid absorption and volume expansion of the material, and is thus not suitable for use as a dressing, etc.